1. Field of the Invention
The present invention relates to a semiconductor opto-electronic device, and particularly relates to a white-light emitting device.
2. Description of Related Art
A light emitting diode has the advantages of longer lifetime, quick response, small volume, energy saving, and low pollution (mercury free), and therefore gradually replaces conventional fluorescent lamps and incandescent bulbs.
A white light is a mixture of several lights, which mainly comprises red light, blue light, and green light. Currently, most white-light emitting diodes consist of a blue chip and a yellow fluorescent powder structure. Although the light-emitting efficiency thereof is satisfactory, the chromatic range is too narrow to cover wide chromatic range.
FIG. 1 is a schematic cross-sectional view of a conventional white-light emitting diode 10. Referring to FIG. 1, a structure of a conventional white-light emitting diode 10 comprises a circuit substrate 101, a chip substrate 106, electrodes 103a and 103b, a hole source layer 107, blue-light active layer 109, and an electron source layer 111. A transparent protective layer 105 comprises a fluorescent powder material (for example, yellow fluorescent powder or red and green fluorescent powder) to protect electrodes 103a and 103b, the hole source layer 107, the blue-light active layer 109, and the electron source layer 111.
The principle of the conventional white-light emitting diode 10 utilizes a fluorescent powder material to absorb blue light from a light source so as to generate a yellow light or red and green light. The yellow light or the red and green light is then mixed with blue light from the blue-light active layer 109 to generate a white light. However, the chromatic range of the conventional white-light emitting diode 10 is narrower, and therefore can not be applied to an apparatus which requires wider chromatic range, such as a display panel.